The present invention relates to a fiber-wired sheet usable for functional optical fiber coils such as optical fiber delay elements and erbium-doped fibers and the like, and a method for manufacturing such a fiber-wired sheet.
Long optical fibers are sometimes used as functional optical fibers such as optical fiber delay elements and erbium-doped fibers. For assembly of an apparatus including a long optical fiber, the optical fiber must be lumped together to be housed in the apparatus. A small bobbin may be used to lump the long optical fiber together. However, using a small bobbin not only makes the entire voluminous but also tends to generate microbending at intersections between the optical fibers and, as a result, may possibly increase the loss.
EPO Publication No. EP1050765A1 discloses an optical fiber holding structure as follows. An optical fiber is arranged in a wound shape with turns displaced from one another in the plane to avoid intersection between portions of the optical fiber. A plurality of turns of the optical fiber are placed in layers at the same position in the thickness direction vertical to the plane in which the optical fiber is arranged. The optical fiber in this state is integrally retained as a sheet with a fixing material such as an adhesive and a film.
The optical fiber holding structure described above being a sheet-like shape as a whole is thin, can be handled integrally without a trouble of coming loose, and can be easily placed in an apparatus. In addition, since the optical fiber is arranged in a wound shape so that no intersection occurs between portions of the optical fiber, the optical fiber can be retained stably without causing microbending and the like.
However, the conventional optical fiber holding structure described above has disadvantages in the aspect of manufacturing efficiency. The optical fiber holding structure is manufactured in the following manner using a manufacturing tool. In the manufacturing tool, two cylindrical winding members for winding an optical fiber are positioned apart from each other by a predetermined distance. A pair of ellipsoidal alignment side plate members are positioned to vertically sandwich the two cylindrical winding members therebetween. One of the alignment side plate members and the two cylindrical winding members are formed integrally. The other alignment side plate member is attached to the cylindrical winding members with bolts or the like. The optical fiber is wound sequentially over the two cylindrical winding members. Upon completion of the winding, the space between the alignment side plate members is filled with a fixing material. The fixing material is hardened to seal the optical fiber with the fixing material as a sheet. The bolts of the manufacturing tool are loosened to detach the alignment side plate member from the optical fiber, and then the optical fiber made integral with the fixing material is released from the manufacturing tool.
As described above, the disclosed optical fiber holding structure requires a complicate manufacturing process. Improvement in manufacturing efficiency is therefore requested.
An object of the present invention is providing a fiber-wired sheet that can be easily manufactured. This object can be attained by the fiber-wired sheet in the first and second aspects and the method for manufacturing a fiber-wired sheet described as follows.
The fiber-wired sheet in the first aspect of the present invention is a fiber-wired sheet including a pair of sheets facing each other and a fiber arrangement sandwiched by the pair of sheets, wherein the pair of sheets have respective adhesive layers on the surfaces facing the fiber arrangement, and the fiber arrangement has a double-layer structure composed of a continuous fiber, and the layers of the structure are in contact with the respective adhesive layers.
Preferably, the fiber arrangement described above has two fiber-arrangement layers and a continuation portion for enabling continuation between the two fiber-arrangement layers, and the continuation portion is formed outside the two fiber-arrangement layers.
Preferably, the fiber arrangement has two fiber-arrangement layers and a continuation portion for enabling continuation between the two fiber-arrangement layers, and substantially no twist is generated on the continuation portion. The state that xe2x80x9csubstantially no twist is generatedxe2x80x9d used herein includes not only the case that no twist is generated at all, but also the case that a twist is generated to a degree of causing no deterioration in polarizing characteristics. For example, a half-turn twist of the fiber will not deteriorate the polarizing characteristics, and thus this is regarded as the state that substantially no twist is generated. In addition, this level of twist will not cause a problem such as breakage.
The layers of the fiber arrangement preferably have roughly the same arrangement pattern. This prevents occurrence of buckling of the fiber.
Preferably, the fiber-wired sheet further includes a single-layer fiber arrangement placed on the outer surface of at least one of the pair of sheets, wherein the single-layer fiber arrangement is composed of a fiber continuing with the fiber arrangement having the double-layer structure and is covered with another sheet having an adhesive layer on the surface facing the single-layer fiber arrangement.
Preferably, the single-layer fiber arrangement continues with the fiber arrangement having the double-layer structure via another continuation portion, and substantially no twist is generated on the another continuation portion.
Preferably, the fiber arrangement having the double-layer structure and the single-layer fiber arrangement have roughly the same pattern.
The fiber-wired sheet in the second aspect of the present invention is a fiber-wired sheet including a fiber arrangement having a multilayer structure composed of a continuous fiber and a sheet interposed between adjacent layers of the fiber arrangement, the sheet having an adhesive layer.
Preferably, the fiber arrangement has a plurality of fiber-arrangement layers and at least one continuation portion for enabling continuation between the plurality of fiber-arrangement layers, and the at least one continuation portion is formed outside the plurality of fiber-arrangement layers.
Preferably, the fiber arrangement has a plurality of fiber-arrangement layers and at least one continuation portion for enabling continuation between the plurality of fiber-arrangement layers, and substantially no twist is generated on the at least one continuation portion.
The layers of the fiber arrangement preferably have roughly the same arrangement pattern.
The fiber arrangement is preferably sandwiched by a pair of sheets having respective adhesive layers on the surfaces facing the fiber arrangement.
The method for manufacturing a fiber-wired sheet of the present invention includes the steps of: arranging a fiber continuously on a plurality of sheets having respective adhesive layers, to form single-layer fiber-arrangement layers on the plurality of sheets; and putting two adjacent sheets among the plurality of sheets one upon the other after the arrangement of the fiber.
The step of putting two adjacent sheets may include the step of reversing one of the two sheets with respect to a virtual axis between the two sheets.
The step of putting two adjacent sheets may include the step of rotating one of the two sheets a half turn as is viewed from top.
In the method for manufacturing a fiber-wired sheet of the present invention, a fiber-wired sheet can be manufactured with substantially no twist generated on the continuation portion for enabling continuation of the fiber-arrangement layers of the fiber arrangement. Specifically, substantially no twist will be generated on the continuation portion by a manufacturing method adopting either of the following four patterns.
(1) A half-turn twist is applied during arrangement of the continuation portion, and a half-turn twist in the direction opposite to that of the twist during the arrangement of the continuation portion is applied when the sheets are put one upon the other.
(2) No twist is applied during arrangement of the continuation portion, and a half-turn twist is applied when the sheets are put one upon the other.
(3) No twist is applied during arrangement of the continuation portion, and no twist is applied when the sheets are put one upon the other, either.
(4) A half-turn twist is applied during arrangement of the continuation portion, and no twist is applied when the sheets are put one upon the other.
The way of applying a twist to the continuation portion and the way of applying no twist to the continuation portion will be described in detail in the embodiments to follow.